1. Field of the Invention
The present invention relates to a fuel reforming apparatus, and, more particularly, to a fuel reforming apparatus suitable for use in a fuel-cell power apparatus which is compact and of which rapid load-following characteristics are required.
2. Statement of the Related Art
A fuel reforming apparatus disclosed in U.S. Pat. No. 4,098,589, for instance, is known as a fuel reforming apparatus for use in a fuel-cell power apparatus which is compact and of which rapid load-following characteristics are-required, unlike fuel reforming apparatuses that are conventionally used in the chemical industry. In the fuel reforming apparatus of this patent, a reaction tube is made compact by improving the heat conductivity between the reaction tube on the one hand, and a combustion gas and a reforming gas on the other. Consequently, the fuel reforming apparatus is made compact and the load-following characteristics are improved.
In the above-described prior art, a reaction tube is provided in a central portion of a fuel reforming apparatus, and a combustion gas is circulated through the reaction tube. These portions are surrounded by a heat insulating layer to prevent the radiation of heat. However, since the combustion gas and the heat insulating layer are disposed adjacent to each other, there has been a drawback in that the heat insulating layer tends to become thick, and the proportion of the heat insulating layer in the fuel reforming apparatus is large. In addition, the combustion gas heats a wide area inside the heat insulating layer, and no consideration has hitherto been paid to the loss of the quantity of heat of the combustion gas involved in the heating thereof.